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weekendmechanic

1998 yz400f Engine head swap to 2000 wr400f, is it compatible?

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I have a 00' wr400f that needs a cylinder head swap. I found one online that looks nearly identical, but it's out of a 98' yz400f. Is it compatible to make the swap?

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I have a 00' wr400f that needs a cylinder head swap. I found one online that looks nearly identical, but it's out of a 98' yz400f. Is it compatible to make the swap?

I also found a 2001 yz426 cylinder head that looks compatible to swap as well, but I'm not sure. If someone could clarify I'd appreciate it, thanks.

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Both will work.  The 00 and older heads have stainless steel valves...the 01 has Ti, which aren't as durable.  The 99 and 98 heads have a nipple on the L/H side near the carb attach boss for the hot start "octopus".  On 00 and up, hot start was incorporated into the carb, so the nipple isn't there (but the un-drilled, un-tapped boss remains).  If you use the '98 head, you can either just put a vacuum cap over the nipple, or pull the nipple out and tap the hole for a 5mm bolt, and plug it.  If you go for the 01 head, be sure to take a really close look at the valves and seats for wear and/or damage...there are several threads here on TT with pics showing what to look for.

 

FWIW, I have a 98 head on my 01 426 with stock SS valves, springs, etc.  It was ported by Eric Gorr, but the original owner never paid nor picked it up...fits fine and works like a champ.

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